The present invention relates to multi-spindle machine tools of the kind comprising a plurality of tool-carrying spindle heads stored in at least one magazine, said spindle heads being exchangeable as desired for the purpose of performing a tool change, a selected spindle head in the magazine being substituted for the one currently secured to the spindle head carrier, this latter spindle head being released from the carrier and conveyed to its predetermined position in the magazine, whereas the other spindle head selected in each case is withdrawn from the magazine and secured to the spindle head carrier. Hereinafter, such a machine tool will be referred to as "of the kind described."
Arising out of the problem of keeping idle periods and thus production periods as short as possible, it is of decisive importance among other considerations in the case of machine tools of this nature, to replace the spindle head currently on the carrier in the operating position with another for the next machining operation as rapidly as possible.
This period required for tool change-over primarily also depends on the nature and operation of the magazines storing the spindle heads. Most of the conventional magazines fundamentally comprise a storing conveying track on which the magazines are installed in recumbent or suspended position, in series and/or mutually parallel. An arrangement in series presupposes that the sequence of the spindle heads which must be held available in the magazine is mandatorily tied to the sequence of the different machining operations. On the other hand, a magazine system in which the spindle heads may optionally be selected individually and recalled as required, is somewhat more flexible.
In this system comprising a series and parallel arrangement of the spindle heads and furthermore in the case of all other known spindle head magazines, it is irksome that wherever it is required to change a spindle head not only the two spindle heads actually taking part in the operation, but either all or at least more than two spindle heads must be displaced, placed in new positions and even regrouped in certain instances. This brings about certain disadvantages or difficulties in that upon replacing tools, the next spindle head must normally be deflected from a horizontal trajectory in the magazine into a vertical trajectory towards the carrier, whereas the spindle head which is to be replaced must describe an oppositely directed trajectory beforehand or even simultaneously. It will be understood that directional changes of this kind require comparatively complex and expensive guiding and conveying means for the spindle heads which are to be so displaced, and that in view of the considerable distance to be travelled between the spindle head support on the spindle head carrier and the magazine storage points in question, some consideration time will be taken up to carry out a tool change, which has an unfavourable effect because it is an unused idle period.
It is an object of the invention to provide a multi-spindle machine tool which speeds up tool changing and in an uncomplicated manner without having to displace more than two spindle heads. It is a further object to make the distances between the storage points and the support of the spindle head carrier extremely short and to make it possible to enable the transfer of the spindle heads from the magazine to the carrier and vice versa to be made along straight trajectories and consequently with uncomplicated driving and guiding means.